Alaska's most urban whales have yet to show any meaningful increase in numbers, evidence that recovery remains elusive for the endangered population despite numerous protective measures imposed in recent years. On the plus side, the Cook Inlet beluga population has not declined notably in the past two years, scientists say.

That represents barely any change from the previous estimate of 340 animals, from 2014, but far below the 1,300 belugas that scientists say were swimming three decades ago in the silty, salty water between Anchorage and the Gulf of Alaska.

"Cook Inlet belugas are still in danger of extinction because the population is so small," said Paul Wade, head of Cook Inlet beluga research at NOAA's National Marine Fisheries Service. "The population trend over the last 10 years has been relatively stable compared to the steep decline seen in the 1990s, but there is some evidence the population has continued to decline slightly. We are concerned that the population is not yet increasing towards its former abundance level," Wade said in a prepared statement.

The newest population estimate comes from the latest in a series of regular aerial counts conducted by NMFS. The estimate is based on thousands of photographs taken from the air a year ago; analysis of those images is a laborious process, so the count that emerged required a full year of work and review, officials said.

Whether the number is a good or a bad sign is in the eye of the beholder, said Phillip Clapham, a cetacean program manager at NMFS' Alaska Fisheries Science Center.

"Optimism depends on whether you look at the glass half full or empty. Former would note that the situation with this population isn't notably getting worse. Latter would say it's not recovering either," Clapham said in an email.

Over the past 10 years, the population has been falling at a rate of 0.5 percent a year, though with variations along that trend line, the population report said.

One ominous sign is what the new population report refers to as "range contraction" — the dwindling spaces in the Inlet that the belugas are using. During the time of the aerial surveys, the belugas were mostly congregating on the west side of the Inlet's upper reaches, according to the report.

The Susitna River Delta, a braided, watery fan at the northern tip of the Inlet, is a particularly important place for the fish-eating belugas in early summer. Since 2008, when the population was listed as endangered and some human restrictions were imposed in beluga habitat, 81 percent of Cook Inlet's belugas have been found in that area in early June; in past years, about half the population was in that region at that time of the year, the report said.

That trend is worrisome, Clapham said.

"The range contraction is significant and does make them more vulnerable. It's not clear why this population has contracted its range, and some research is underway to try to understand that; presumably much of the distribution is driven by prey availability," he said by email.

The delta, rich with salmon and eulachon that belugas eat, is also known as a calving site for the whales.

The sites where belugas were found are within the 3,013 square miles of critical habitat that was designated by NOAA in 2011, in accordance with Endangered Species Act requirements. That critical habitat, mostly on the northern part of the Inlet and along the western coastline, holds the areas considered to be most important to the belugas and, potentially, most worthy of additional safeguards.

Cook Inlet belugas were listed as endangered after numbers crashed in the late 1990s.

Overhunting in the 1990s by the region's indigenous residents — who have the right to harvest marine mammals under federal law — is believed to have been the catalyst for the precipitous decline.

Hunting was largely halted in 1999, but the expected annual population rebound of 2 percent to 6 percent did not materialize. Other environmental problems, possibly several of them intertwined, appear to be keeping the population depressed, according to a NMFS recovery plan issued last year.

With hunting pressure gone, the most serious threats to the belugas are probably catastrophic events like mass strandings or an oil spill, high amounts of underwater noise that interfere with communications and the cumulative impacts of environmental problems, including climate change, according to the recovery plan. Other potential threats are disease agents like pathogens and harmful algal blooms, habitat loss, reduction in food sources, illegal hunting, pollution and predation, according to the recovery plan.

Environmentalists pushed for Endangered Species Act protections for belugas. The latest population numbers show that the belugas' problems continue nine years after the endangered listing, said Bob Shavelson, advocacy director for Cook Inletkeeper, a regional environmental group.

"I think it's clear the population's not rebounding like the National Marine Fisheries Service predicted it would," he said.

Despite the endangered listing, and the official "depleted" designation granted prior to that under the Marine Mammal Protection Act, little has changed to improve conditions for Cook Inlet belugas, Shavelson said.

"I've seen zero change in industrial behavior in Cook Inlet. Seismic activities go on unabated. Sewage discharges continue without control," he said. "The complexities of our ecosystem are so high and our laws are so rigid and limited that it's not a surprise that business as usual prevails."

Several industry and pro-development groups opposed the listing, arguing that it would interfere with commerce in Alaska's most populous region, which includes oil and gas production and cargo shipping. They also objected to the designation of critical habitat, which was made final six years ago.

Now, several years after those formal designations, the population report shows some glimmer of good news for belugas, said Carl Portman, deputy director of the pro-industry organization Resource Development Council.

“We’re encouraged that the population is stable,” he said.

Joshua Kindred, environmental counsel for the Alaska Oil and Gas Association, also saw some positive signs — with caveats.

“It’s good in a sense that we’re not seeing a decline,” he said. “More activity in Cook Inlet hasn’t necessarily hurt the population.”

But Kindred cautioned that populations are difficult to count in the silty Inlet and that year-to-year variations might be attributed to statistical “noise,” or effects other than actual births or deaths of whales. And the lack of a population rebound is still concerning, he said. He hopes to see better population numbers in the future, he said.

The aerial surveys were done annually from 1993 to 2012 and have been conducted biannually since then.